兼具换相电压补偿和直流电流抑制能力的电网换相换流器拓扑

Topology of Line Commutated Converter with Capability of Commutation Voltage Compensation and DC Current Suppression

为提高传统直流输电系统抵御换相失败的能力,改善系统故障期间的动态特性,提出了一种基于晶闸管型全桥子模块(T-FBSM)的复合型电网换相换流器拓扑,在故障期间可以通过控制工作模式的切换同时实现换相电压的补偿及直流电流增长的抑制,从而提高换相失败的免疫能力。研究了T-FBSM与换流阀的协调控制策略,并设计了T-FBSM电气参数。最后,在PSCAD仿真环境中设置不同仿真案例,验证了所提新拓扑的电压、电流应力及换相失败抑制效果。仿真结果表明,所提复合式电网换相换流器拓扑协调控制策略及所设计的T-FBSM电气参数合理、有效,同时所提拓扑可以有效降低换相失败概率,并可改善系统的恢复特性。

In order to improve the ability of line commutated converter based high voltage direct current(LCC-HVDC) system to resist commutation failures and improve the dynamic characteristics of the LCC-HVDC system during the fault period, this paper proposes a compound line commutation converter(LCC) topology based on thyristor-type full bridge sub-modules(T-FBSMs).The compensation of commutation voltage and the suppression of DC current rise can be realized by switching the control modes of T-FBSM during the fault, which improves the commutation failure immunity. Then, the coordinated control strategy of the TFBSM and the converter valve is studied, and the electrical parameters of T-FBSM are designed. Finally, different simulation cases are set in the PSCAD simulation environment to verify the voltage and current stress and the commutation failure suppression effect of the proposed topology. The simulation results show that the proposed coordinated control strategy of the compound LCC topology and the designed electrical parameters of T-FBSM are rational and effective, and the proposed topology can effectively reduce the commutation failure probability and improve the recovery characteristics of the system.